1. Field of the Invention
The present invention relates to a colorant-containing curable composition for producing a color filter which can be suitably used in a liquid crystal display or a solid image pickup device (such as CCD and CMOS) to form a colored image, a color filter produced with such a composition, and a method of producing such a color filter.
2. Description of the Related Art
It is known that color filters for use in liquid crystal displays or solid image pickup devices are manufactured by a dyeing method, a printing method, an electrodeposition method, or a pigment-dispersing method.
The pigment-dispersing method is a method of producing the color filter by a photolithographic method with a colored radiosensitive composition comprising any photosensitive composition and a pigment dispersed therein. Such a method using a pigment is advantageously stable against light, heat or the like. The pigment-dispersing method, which includes patterning by a photolithographic method, has high positioning accuracy and thus has widely been used as a suitable method for producing color filters for use in large-screen or high-definition color displays.
The pigment-dispersing method may include the steps of forming, on a glass substrate, a coating layer by applying the radiosensitive composition with a spin coater, a roller coater or the like and drying it, exposing the coating layer to light to pattern it, then developing it to form colored pixels, and repeating such a process with respect to each color, so that a color filter is produced.
Specifically, as the pigment-dispersing method a negative-type photosensitive composition comprising an alkali-soluble resin, a photopolymerizable monomer and a photopolymerization initiator is conventionally known (for example, see Japanese Patent Application Laid-Open (JP-A) Nos. 02-199403 and 05-273411).
In recent years, there has been a demand for a higher definition of the color filter for use in the solid image pickup device. However, the conventional pigment dispersing system is not suited for such a fine pattern-requiring application as the solid image pickup device, because it cannot improve a resolution and has a problem that coarse particles of the pigment can cause color irregularities or the like. In order to solve the problem, some known methods use a dye (for example, see JP-A No. 06-75375).
However, a dye-containing curable composition can have any of new problems (1) to (4) below or the like.
(1) General dyes have low solubility in either an aqueous alkali solution or an organic solvent, and thus it would be difficult to obtain a liquid curable composition having a desired spectrum.
(2) Many dyes can interact with another component of the curable composition, and thus it can be difficult to control the solubility (development characteristic) of the cured part and the uncured part.
(3) If the dye has a low molar extinction coefficient (ε), it must be added in a large amount of the dye so that the amount of any other component such as a polymerizable compound (monomer), a binder and a photopolymerization initiator in the curable composition must be reduced and so that the composition can have a problem such as a reduction in curability, post-curing heat resistance, and development performance of the (un)cured part.
(4) Generally, dyes are inferior to pigments in light fastness or heat resistance.
In contrast to use in the production of, a layer thickness of not more than 1.5 μm is particularly required for use in the production of color filter for solid image pickup devices. Thus, the curable composition should contain a large amount of dye and thus can have the above problem.
Due to these problems, it has been difficult to satisfy the practically required performance with respect to the colored pattern of a fine and thin layer for a high-definition color filter.
Specifically, concerning magenta dyes, there is a proposal of a red ink composition for use in a color filter, which contains a γ acid-phenylazo type or phenylazonaphthalene type dye (for example, see JP-A No. 09-291241). However, it is difficult for such a dye to satisfy both heat resistance and light fastness.